Stem cells hold tremendous promise for the treatment of various incurable diseases by transplantation therapy. Of the various stem cell types, hematopoietic stem cell (HSC) transplantation has been the most successful in the clinic. Since the introduction of bone marrow HSC transplantation in 1968, HSCs have been used in the treatment of hematopoietic diseases such as leukemia, lymphoma, thalassemia and autoimmune disorders. HSC transplantation has also been shown to produce promising results for the treatment of chronic liver failure and acquired immunodeficiency syndrome.
HSCs are obtained from many different sources such as bone marrow (BM), peripheral blood (PB) and umbilical cord blood (UCB). HSCs isolated from the UCB have several advantages for transplantation therapy compared to the BM and PB. They are easily collected and stored in cord blood banks, have lesser risk of graft versus host disease (GVHD) in transplant recipients due to their immune naivety and require less stringent criteria for donor-recipient matching. Additionally they have high proliferation rates, autocrine production of hematopoietic factors and longer telomere lengths due to their younger chronological age.
However, a major limitation to their use in transplantation is the low cell numbers in a single UCB unit. The yield of HSCs from a single freeze-thawed UCB unit is typically about 1.0×107 cells. This number is far less than the recommended cell numbers required for transplantation. Recommended cell numbers range from 2.5-5×106 CD34+ cells/kg for a successful engraftment. As such, single unit UCB-derived HSC transplantation is often a challenge for the treatment of adults.
Thus, a need to increase stem cell numbers UCB units (e.g., a single UCB unit) is needed.